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(o) June 22, 1965 SHINTARO OSHIMA ETAL 3,191,053 SIGN DETECTING SYSTEM Fiied Aug. 19, 1960 6 Sheets-Sheet 6

3,191,053 United States Patent Office Patiented June 22, 1965

2 FIG. 4 is a wave diagram for showing an example of 3,191,053 control time chart for describing the operating principle SIGN DETECTING SYSTEM of the system of the present invention; Shintaro Oshima, Tokyo-to, Hajime Enomoto, ichikawa FIGS. 5 (A) and (B) are characteristic curves for de shi, and Shiyoji Watanabe and Yasuo Koseki, Tokyo-to, 5 scribing an operation principle of the system of the Japan, assignors to Kokusai Denshin Denwa Kablishiki present invention; Kaisha, Tokyo-to, Japan FIGS. 6 (A) and (B) are embodiments of windings Filed Aug. 19, 1960, Ser. No. 50,689 wound on magnetic cores to be used in the embodiment 6 Clains. (C. 307-88) of the present invention; The present invention relates to a sign detecting sys 10 FIG. 7 is a connection diagram for showing the other tem, more particularly to a system for detecting the plus example of the present invention; or minus polarity of the difference between a direct-cur FIG. 8 is a connection diagram for showing another rent input signal and a direct-current reference signal by example of the present invention; the use of non-linear elements having substantially a FIG. 9 is a characteristic curve for describing the oper symmetrical hysteresis characteristic with respect to its ation of the example shown in FIG. 8; original point as ferro-magnetic cores or ferro-electric FIG. 10 is a characteristic curve for the describing op material. eration of another example of the present invention; In the above-mentioned system, it is necessary for FIG. 11 is a connection diagram for showing an ap precisely detecting the polarity of an electric signal that plication of the system of the present invention; a detecting means including the non-linear elements is - FIG. 12 is a connection diagram of another example unaffected by the preceding polarization of the non-linear of the present invention; - elements even if the hysteresis of said polarization has FIG. 13 is a connection diagram for another example passed along any course. This fact is most important for of the present invention; the sign detecting circuit. Hence, it is necessary for con FIGS. 14 and 15 are connection diagrams for showing structing a precise analogue-digital converter to select 25 other examples of the present invention; only non-linear elements each having an original point FIG. 16 is a connection diagram for describing the which has no relation to the prior hysteresis of the principle of the present invention; polarization. The original point will be denoted herein FIGS. 17 and 18 are views for showing operation of after as "zero point.” the system of the present invention in FIG. 16; The drift of the zero point makes it difficult to obtain 30 FIGS. 19 and 20 are connection diagrams for showing an analogue-digital converter having great accuracy. other examples of the present invention. The present invention further relates to a system for The principle of the present invention will be first de converting the sign of a direct-current signal to an alter scribed in connection with FIG. 1. The circuit of FIG. nating-current high frequency signal having a "0 phase' 1 consists of two ferro-magnetic cores M and M2, three or “it phase.' It has been well-known, in one of such 35 windings N1, N2 and N3, an input impedance Z connected systems as described, above, to employ a magnetic ampli to the winding N1, and an output impedance Zo connected fier obtaining a double frequency of the energizing cur to the winding N. Each of the windings N1, N2 and rent thereof. In this magnetic , however, when N3 is composed of a coil wound on the M1 a relatively large direct-current passes through the am and another coil wound on the magnetic core M. pifier, a residual magnetism will be created in the core 40 As shown in FIG. 1, the windings N1, N2 and N are or cores of the magnetic amplifier by the direct-current wound in such a manner that all coils of the windings N due to the hysteresis characteristic of the magnetic core, and N are wound on the magnetic cores M1 in the same and the residual magnetism will remain in the magnetic polarity, and one coil of the winding N is wound on the core or cores for a long time. This defective character same polarity, as that of the coils of the windings N istic appears always in a device using a ferro-magnetic and N on the core M1 and the other of the winding N. material or ferro-electric material. Hence, it is generally is wound in the reverse polarity as the windings N and difficult to construct a very precise sign detecting device No on the core M2. having a very stable zero point. - The operation principle for getting an even harmonic An essential object of the present invention is to obtain frequency of the exciting current is as follows. In the a very precise sign detecting circuit having a very stable 50 circuit of FIG. 1, let it be assumed that the magnetization Zero point. characteristics of the cores M1 and M2 are such as shown in FIG. 2(a). The novel features which are believed to be character Then, when an input signal current Is is impressed on istics of the present invention are set forth with particu the winding Ni and a high frequency exciting current if larity in the appended claims, but the present invention, 55 is applied to the winding N and the amplitude of the both as to its construction and manner of operation, to current it is sufficiently large enough, to make operation gether with further objects and advantages thereof, may along the major hysteresis loop of the cores M1 and M. be understood by reference to the following description possible, as shown in FIG. 2(b), where the solid line is taken in conjunction with the accompanying drawings, the wave form of the exciting current if for the core in which the same members are indicated by the same 60 M1 and the broken line is the wave form of the exciting numerals, and in which: current ii.2 for the core M2. FIG. 1 is a connection diagram for describing the Then, the output voltages are induced across both of principle of the present invention; the output coils wound on the cores M and M, respec FIG. 2 is a characteristic curve and wave diagram for tively, thus inducing an output voltage across the termi describing the operation of the circuit shown in FIG. 1; 65 nals of the winding N. FIG. 3 is a connection diagram of one example of the The states of the output voltage across the terminals present invention; of the winding N varies according to the polarity of the 3,191,053 3 4. input signal current Is in this case, there are three transiently a sufficiently large ; or alternating States. current; in such a manner that both of the absolute values (i) If Is=0, then, the induced voltages across respec of the residual magnetisms of the magnetic cores become ?tively the output coils of the cores M1 and M2 always are the value Ho. equal amplitude and just opposite phases, so that no In FIG. 3, an input signal winding M1, an exciting wind voltage is induced across the terminals of the winding ing N and an output winding N are wound on two ferrite N as shown in FIG. 2(e). cores M and M2 having Substantially symmetrical hyster (ii) If Isè0, then, the induced even harmonic voltage esis characteristics with respect to their original zero V induced across the output coil of the core M1 becomes points. larger than that of the core M2 and both of the induced 10 The effect of the setting signal in this invention will be voltages are in phase, so that the even harmonic frequency explained in connection with FIG. 3, as follows. As we voltages ea of the exciting current are induced across have described above, the setting signal is indispensable the terminals of the winding N as shown in FIG. 2(f). for attaining precise detection of a sign, and the setting And in this case, the even harmonic components in the signal may be an alternating current signal, a direct output signal have '0' phase as shown in FIG. 2 (f). current signal or a superimposed signal of said alter (iii) On the contrary, if Is<0, then, the induced even nating current signal and said direct current signal, but harmonic voltage V across the output coil of the core M for simple explanation we consider only the case where becomes larger than that of the core M1 and both of the the alternating current signal is used as a setting signal induced voltages become in phase, so that the even har hereafter. . monic voltages eat of the exciting current are induced 20 As shown in FiG. 3, the windings N1, N2 and N3 are across the winding M3, and the even harmonic components wound in such a manner that all coils of the windings N1 of the output voltage have a at phase, as shown in FIG. and Ns are wound on the magnetic cores M1 and M2 in 2(g). the same polarity, and one coil of the winding N2 is From the above descriptions, the phase of the even wound in the same polarity as that of the coils of the harmonic components in the output voltage induced across windings N and N on the core M1 and the other coil of the winding N is completely dependent on the sign of the the winding N is wound in the reverse polarity as the input signal. windings N and N3 on the core M2. Then, if we detect the phase of the even harmonic An input signal current Is is applied to the winding N1 components of the output voltage across the winding N3, through an input resistor Ri, and a demagnetizing signal we can detect the sign of the input signal. 30 current id having a high frequency f' and an exciting sig When it is assumed that the magnetic cores M1 and M2 nal current it having a high frequency fare successively have such B-H characteristic having no hysteresis as applied to the winding Na. shown in FIG. 2 there is no drift of the Zero point of the A resistor R is a coupling resistor, and a capacitor C magnetic core. Generally, however, a magnetic Sub and an L construct a parallel tuned circuit for a stance has a hysteresis characteristic. This hysteresis ef 3 5 frequency of 2f. fect, as shown in FIG. 2, is equivalent to the case wherein The output signal having the frequency of 2f is led a zero point displaced by AH from the prior Zero point out through the secondary windings of the tuned circuit. is taken as the new zero point. The magnetic field inten We consider the case where the currents shown in FIG. sity AH is due to the effect of the preceding signal. How 4 are applied to the circuit of FIG. 3. ever, if two magnetic cores M1 and M2 are combined in 40 A demagnetization current ia (referred to as a setting such a manner that the displacements AH1 and AH2 of signal in this invention) is a gradually damped high fre magnetic field intensities in the magnetic cores M1 and quency exciting signal, and its peak amplitude is large M. due to their preceding hystereses take the following enough to cover the coercive force of the magnetic core. relations just before the sign detection, then According to said setting operation by the current id the residual effects of the preceding signals (AH1 and AH) for cores M and M2 become, respectively, zero, and both the resultant displacement AH becomes to AH--AH2=0, of the cores M1, M2 are reset to zero point. whereby drift of the zero point can be completely elimi Next, the sampled input signal Is and the exciting cur nated. rent of high frequency fare simultaneously applied to the The present invention relates to a new sign detecting windings N1 and N2, respectively. system in which the resultant residual magnetism is always Then as explained with reference to FIG. 2, even har made zero just before the sign detection so as to eliminate monic voltages are induced across the winding N. the above mentioned drift of the Zero point by using a In this case only the double frequency component is se setting signal. lectively tuned with the circuit (LC) and the double Among two conditions (AH1=AH2=0 or AH= -AH2) 5 5 frequency voltage whose phase corresponds to the polarity for eliminating the resultant residual magnetism, the con of the input signal is obtained at the output terminals dition (AH=AH=0) can be obtained by impressing on through the coupling resistor R. . the cores, a gradually damped alternating magnetic force The demagnetization is performed by using the setting as a setting signal, having an amplitude which is Sufi Signal as described above, that is, the deviation AH be ciently larger than the coercive-force of the magnetic 60 cores just before the sign detection so as to eliminate com comes Zero, and when an exciting signal current it and pletely the resultant residual magnetism. Demagnetiza the input signal Is are applied simultaneously to the tion is performed through this process. The condition above-mentioned elements of FIG. 3, the input signal is (AH=AH2=0) can also be obtained by making the converted to an even harmonic voltage without any drift component in the direction of the magnetic field due to in 65 of the zero point. - ...... put signal current applied to the input winding Zero by Let it be assumed that the magnetic characteristics using a setting signal which is employed to direct the po of the magnetic cores M1 and M2 are such as shown in larity of the residual magnetism towards the direction FIG. 5(A). Then, when the input signal of direct cur perpendicular to the magnetic field generated by the input rent Is is supplied to the winding N and the high fre signal current and the output current winding wound on 70 quency setting current id is supplied to the winding N. the magnetic cores. the amplitude of the current is being sufficiently large so - For obtaining the condition (AH= -AH2=Ho) in the as to produce. a sufficiently larger magnetic field than the circuit of FIG. 1, it is only necessary to supply both a coercive force. He and the attenuation locus of said ampli certain direct-current of a constant value and an alternat tude describing a gentle envelope such as shown in FIG. ing current to the exciting winding Na or to impress 75 5 (B), a residual magnetism (b will remain in the mag 3,191,058 S 6 netic core M1 when the current it becomes zero and the teristic of Said element irrelevant to the magnitude of the current Is also becomes zero. residual magnetism, and by detecting the phase displace On the other hand, since the current is is the reverse ment of the output voltage eaf. By such a method as de phase against the former case relative to the magnetic Scribed above, it is possible to discriminate the polarity core M2, an inverse excitation is given to the core M of very small input current in a highly precise manner. as shown in FIG. 5(B) by broken line. However, the The above description relates to the case in which polarities of the residual magnetisms of the magnetic ferro-magnetic elements are used, but the same princi cores M1 and M2, are the same to each other because the ple as the above-mentioned magnetic elements can be current Isg is supplied to the cores in the same polarity. easily applied to the case in which ferro-electric elements Then, we consider the case where the continuous input 0 are used in the place of ferromagnetic elements, by ex signal current is is applied to the input signal winding. changing the electric voltage for the electric current. An The frequency of the input signal Is is much lower example of such a case is shown in FIG. 7, in which the than that of the setting signal frequency and the excit circuit consists of the ferroelectric elements C1 and C2 ing signal frequency, and is also lower than the repeti having the same symmetrical nonlinear characteristic, two tion cycle of the exciting signal. coupling condensers C1 and C2 having the same capacity, After application of the setting signal, both of the two damping resistors Rd1 and Rd having the same cores M1 and M2 are magnetized to a certain magnitude resistance, an output T of balance type, input of residual magnetism corresponding to the magnitude terminals 1 and 2, and output terminals 5 and 6, said of the input signal at the setting period, so that when members being connected as shown in FIG. 7. an exciting signal is applied to the elements, the input 20 In the circuit of FIG. 7 also, such elimination of the signal at the exciting period and the residual magnetism residual polarization and establishment of the symmetri effect induce even harmonic output voltages; then a cal condition of the zero point as in the case in which high accuracy in analogue-digital conversion is attained. ferro-magnetic elements are used, can be attained by In the case where the sampled input signal is applied impressing a depolarizing electric voltage on the ter to the elements, there is no input signal at the setting minals 3 and 4, and then by impressing an input voltage period and the setting effect results in no resultant of the and a high frequency exciting voltage, respectively, on the preceding input signal and sign detection will be attained terminals , 2, and 3, 4. In this case, an even order higher at the next sampling period without any drift of the zero harmonic voltage of the exciting signal is generated point. On the contrary, in the case where the con in a closed loop circuit consisting of the members tinuous input signal is applied to the elements, a certain C1-C1-Rd1-T-R2-C-C2. The phase of the magnitude of residual magnetism flux corresponding to generated higher harmonic voltages becomes 0 or it phase the input signal of the setting period remains. That is, in accordance with the polarity of the input signal, these the cores M1 and M2 memorize the magnitude of the voltages are led out of the output terminals 5 and 6. In input signal in the state of residual magnetism, and at the closed loop circuit, when capacities of the capaci the next sampling period the input signal, to be added 3 5 tors C and C2 and inductance of the primary winding of adding with the said residual magnetism, determines the the transformer T are so selected that the circuit resonates phase of the even harmonic output voltage more quick with the second harmonic of the exciting wave, a voltage ly and more precisely in comparison with the case of sam e having frequency 2f appears at the output terminals pled input signal. 5 and 6. As explained before, there is another method to cb 40 The description of FIG. 3 relates to the case in which tain the condition (AH1=AH2=0) for the elimination only the input current is and the exciting current it hav of the residual magnetism of the preceding input signal. ing frequency fare supplied, respectively, to the wind As shown in FIG. 6, the direction of the setting mag ings N1 and N2. However, besides the currents one high netization is perpendicular to the direction of magnetiza frequency current iro having frequency fo may be applied tion generated by the input signal current and the excita 45 to the winding N2. In this case, a modulation product tion signal. of frequencies (f--f) and (f-f) will be obtained out Accordingly, when a direct current pulse signal, whose of the output terminals of the winding N3. When one amplitude is large enough to cover the coercive force in of the modulation components is selectively taken out, the setting field direction, is applied, at the setting time it is possible to obtain an electric output voltage having the residual magnetism of the preceding input signal is one of two possible phase positions which differ by 180° effectively eliminated, and there is no drift of the zero to each other in accordance with the polarity of the input point for the next sign detecting period. current Isg. For the simplification of the explanation, we describe We have described a circuit capable of detecting the the case in which, as shown in FIG. 3, a selective res polarity of a small, weak signal by utilizing ferro-mag onant circuit LC tuned to a frequency 2f which is twice 5 5 netic or ferro-electric elements having a symmetrical the exciting frequency f is connected in cascade to the hysteresis characteristic. However, in the circuit, it is output winding N through a coupling resistance R, possible to obtain an even order higher harmonic oscilla and an output voltage having frequency 2f is led out of tion by feeding back a particular even order higher har the output terminal. In this case also, as described monic component to the input signal is by means of an above, the polarity of the output voltage ear becomes “0” 60 internal feedback or an external feedback of the higher phase or "r" phase in accordance with the positive or harmonic. In this case also, the oscillation phase is con negative polarity of the input current Is, and moreover, trolled by the polarity of the input signal s, whereby when the frequency of the exciting current it is selected the polarity of the input signal is can be discriminated. so as to be sufficiently large in comparison with that of In the following will be described the case of a second the input signal current Is, and the number of turns of harmonic oscillation. FIG. 8 shows a connection dia the windings N and Ns are suitably selected, a large volt gram for illustrating the principle of a circuit which can age gain due to the difference between the frequencies detect the polarity of the input current according to the of the currents if and Is will be obtained. Accordingly, oscillation such as described above. it is possible to detect the sign of the small signal input The circuit of FIG. 8 consists of a pair of ferro-mag current Is by amplifying and demodulating the output 70 netic cores M1 and M2, an input winding N1, an exciting voltage ear. According to the present invention, by sup and setting winding N2, an output winding N, a capacitor plying a setting signalia to the exciting winding before C, and a coupling resistor R. The windings are wound supply of the exciting current if and the signal input cur on the cores in such a manner that the winding N and rent is so as to establish the intrinsic symmetry of the Ns are of the same polarity relative to the cores, M1 and magnetic element to make the magnetic hysteresis charac 75 M2, the winding Ng has the Same polarity as the windings 3,191,058 7 8 N1 and N on the core M1 and the reverse polarity to has no need of so low a value of the distortion factor with the core M2, and all the coils of each of the windings are reference to waveform. connected in series. The following description is in connection with the Let it be assumed that a relatively large exciting cur case in which any level detection is carried out by uti rent it is supplied to the winding N. When input cur 5 lizing the above-mentioned principle. In this case, one rent Is having a suitable amplitude is supplied to the more standard reference signal winding Na having the winding N1, an even order higher harmonic voltage of same polarity as the input winding N is added. This the exciting current it will develop in the winding N3. example is shown in FIG. 11, in which windings N, Na The phase of said second harmonic voltage is determined and N3 of a plurality of unit circuits as shown in FIG. 8 by the polarity of the input signal current Is. And if O are connected respectively in series and each unit circuit the second harmonic voltage is generated, a second har is coupled to a respective P1, P2 . . . Pn. monic oscillation will be built up in the output circuit The oscillation frequency of the second high harmonic consisting of the winding N3 and the capacitor C. This of the exciting current it is selected so as to be equal to generation is caused by a so-called parametrical oscilla the oscillation frequency of the respective parametron. tion. The oscillation phase is subjected to the induced in the circuit of FIG. 11, when a standard direct current voltage. If the input current is varies a positive value ist is supplied to the circuit consisting of standard wind from a negative value, the oscillation phase of the output ings N4, 2N. . . . nN4 of the unit circuits, and a signal second harmonic voltage e2f reverses abruptly as shown input current is is supplied to the input winding N1. The in FIG. 9. This fact has been proved by the inventors' coils having the same number of turns and phases of the experiments. oscillation frequency in the windings INs, 2N. . . . nN In FIG. 9, the input current is and the second high coupled with the P1, P2 . . . P change suc harmonic output voltage eat are, respectively, taken on the cessively from -phase to -phase in accordance with the abscissa and ordinate. In this characteristic curve, the magnitude of the signal current flowing through the input amplitude of the voltage eaf is nearly constant between winding N1 with successive increase of the signal input points a and b or points c and d irrespective of the direc current Is, because the number of turns of the winding tion of the current Is, but there is a hysteresis phenome iN4, 2N4 . . . in NA increase successively in their numeri non between the points b and c. The phenomenon is due cal order. Accordingly, if the oscillation phases (--) to the effect of the prior oscillation. and (-) of the parametrons are made to correspond to As described before, if the setting signal id is applied the binary digit 1 and 0, respectively, the level of the sig just before every exciting signal to the winding N2 of 30 nal can be directly converted to a binary digit. the circuit of FIG. 8, said drift of the zero point is elimi In the example of FIG. 7, when the standard reference nated completely, that is, a difference AI between said direct cuirrent Ist is impressed in common on all the unit signals Is and is becomes zero in FIG. 9, and we can ob circuits and effective ampere turns of the windings INA, tain such an experimental relation between the input sig 2N. . . . nn are set so as to be able to vary optionally, nal and the second higher harmonic voltage as shown in 3. 5 for example, by parallel connecting resistors one by one F.G. 10. on the winding IN4, 2N4 . . . nN, the input current On the other hand, if such setting signal id and the ex Is can be converted to a sign signal in any optional rela citing signal it as shown in FIG. 4 are applied to the cir tionship. Moreover, in the example of FIG. 11, a large cuit shown in FiG. 8, we can easily realize a highly sensi and a Small magnitude of the currents Ist and Is are made tive and high accurate sign detecting circuit. to correspond, respectively to the 0 phase or the ar. phase As described above, when in the circuit of FIG. 8, an of the oscillation frequency and led out of the parame exciting current it and an input signal current is are Sup trons. However, magnitudes of the currents Is and Is plied, respectively, to the windings N2 and N1, a second can be led out as the positive or negative polarity of a high harmonic oscillation the phase of which is controlled direct current or voltage by synchronous detection of the by the poiarity of the small signal input current Is is oscillation phase of the output voltage having fre produced in the output winding N3, whereby a Second quency 2.f. high harmonic voltage of large amplitude is obtained and The above-mentioned principle can be applied to a de the oscillation phase of the voltage can be surely con tecting circuit utilizing ferroelectric elements. In FIG. trolled by the polarity of the small signal input current 12 is shown a basic circuit for obtaining a frequency s. The phase of the second high harmonic voltage cor doubler by utilizing a parametric oscillation of a a circuit relates mainly to the distortion of the symmetry of the including two ferroelectric elements. The circuit of FIG. nonlinear characteristic of each element and has no rela 12 consists of two ferroelectric elements C1 and C, tion to the unbalance between two nonlinear elements. two condensers C for choking the standard reference Accordingly, variation of the characteristic of each in direct current voltage Est and the signal direct current dividual nonlinear element has no direct relation to the 5 Voltage Esg, one coupling resistor R1 for impressing the establishment of the oscillation phase of the second high voltage Esg on the elements Cy1 and C2, the other cou harmonic voltage, because generated harmonic current pling resistor R2 for impressing the voltage Est on the components caused by odd high harmonic voltages are elements Cy1 and Cv2, and a coupling transformer T. very small due to the reason that the output circuit is When a high frequency control voltage et having frequen designed so as to be resonant with only the second high GO cy f is impressed on terminals 3 and 4, an output voltage e2f having frequency 2f can be obtained from the secon harmonic component. dary winding of the transformer T. In this example, the By the same reason as above, when the resonant fre Sequence of the voltage e is the same as that shown in quency of the output circuit is chosen to tune with the FIG. 4(A) except that current is replaced by a voltage. frequency (f--fo) or (f-f) in FIG. 8, and the other According to the circuit of FIG. 12, as will be well under exciting signal of a high frequency f. is also applied to stood from the description concerning the circuits of the winding Na at the exciting period, the phase of the FIGS. 3, 7 and 8, the phase of the output oscillation volt output voltage of the frequency (f--f) or (f-f) is sub age eef can be controlled in accordance with the polarity jected to the polarity of the input signal, and a sign detec of the resultant voltage of the voltages Esg and Est. tion of the input signal with high sensitivity and high The above-mentioned examples relate to the cases in accuracy is easily obtained. - which a setting operation is indispendable for detecting In the circuit for obtaining a modulation product of the sign of the applied input signal without relation to two frequencies, the problem that the exciting signal con the preceding applied state. However, when the circuit tains even higher harmonic components makes no trouble is so constructed that the magnetic induced field due to in the sign detection process, so that the exciting signal 75 the input current Is is perpendicular to the magnetic in 3,191,053 gie duced field due to the setting current, and a small signal output winding N3. The polarity of the voltage e1-2 input current is to be detected and an exciting current of is controlled by the polarity of the current Is, because large amplitude are supplied after demagnetization of the the following relation is established. magnetic field induced due to the preceding input current Is the phase of the second higher harmonic output volt 5 er 1+fectsgir1'ite age can be controlled by the instant currents. An ex ample of Such a circuit as described just above is shown Now, if only the voltage effa is selected at the resonant in FIG. 6. circuit LC through a coupling resistor R, it is possible to The above-mentioned example relates to the case utiliz discriminate the sign of the input current Is by detecting ing ferro-magnetic cores, but the same object can be at O the phase of the voltage efits. In this case, since there tained by using ferro-electric elements instead of ferro is a large frequency difference between the voltage magnetic elements and by impressing a direct electric field efife and the current Is, discrimination of the polarity and an alternating electric field on the elements. of a weak low frequency signal Is can be attained with a In FIG. 13, a frequency doubling oscillation circuit large voltage gain. consisting of ferroelectric elements C1 and C2, each The following description is in connection with a sys having two pairs of control terminals which are perpen em capable of carrying out the above-mentioned opera dicular to each other, condensers C and C for choking tion in a very efficient manner. Recently, systems capable direct current, and a coupling transformer T. of carrying out amplification or oscillation by parametri Controlling of the circuit of FIG. 13 can be effectively cal oscillation of particular elements having a nonlinear attained, in the same manner as that of the circuit of 20 character have been proposed. In these systems, how F.G. 6. ever, a particular harmonic oscillation, for instance, the The above-mentioned level detecting system relates to second or third harmonic oscillation of the non-linear ele the case of oscillation, but the same principle may be ment, has been generally utilized as the output power. applied to an amplification or modulation circuit. Strictly speaking, when nonlinear dampers are used for In the above description, only one winding is used for 2 5 obtaining a stable condition unnecessary power is con applying the exciting signal and the setting signal to non Sumed due to the existence of not only a harmonic oscil linear elements. In order to realize a setting action ef lation lower than an intended order but also unnecessary fectively, there are some circuits by which demagnetiza higher harmonics, whereby the total power efficiency de tion is easily and effectively carried out. According to creases. This disadvantage can be eliminated by the fol these circuits a greater accuracy for setting the sign of lowing system which is illustrated in FIG. 16. This il the input signal is easily attained. An example of those lustration relates to a general basis circuit in which two circuits is shown in FIG. 14 in which four magnetic cores ferromagnetic elements are used, and a harmonic oscil are used. iation of double frequency is established by parametrical In the circuit of FIG. 15, an input signal winding N, oscillation of the elements. The circuit includes two an exciting winding N2, on output winding Na and a set ferro-magnetic cores M and M2, an exciting winding N, ting winding NA are Wound on four ferro-magnetic cores an output winding N2, and a condenser C connected to M1, M2, M3 and M4 so that winding polarities of the coils the winding Na in parallel. Now, in the circuit of FIG. of all the windings are the same on one core M1; the 16, when a high frequency electric voltage e is impressed number of coils having the same polarity is equal to that on the exciting winding N1 to cause a parametrical oscil of the coils having reverse polarity on the other core M lation, a second harmonic of the exciting current is gen and the winding polarity of a respective coil of all the erated in accordance with resonance relative to the in windings are reverse on the other cores M and M. ductance of the output winding N2 and the capacitance of The winding polarities of all coils of the windings N the parallel condenser C. That is to say, now, let it be and N are the same and the number of coils having the assumed that the hysteresis characteristics of the mag same polarity are equal to that of the coils having a re netic cores M1 and M2 take the forms as shown in FIG. verse polarity with respect to the windings N and Na. 17(a). In this case, when high frequency magnetic fields In the circuit of FIG. 14, there is no linear coupling be H1 and H. Such as those shown in FIG. 17(b) are merely tween the setting signal ie, the exciting signal it, and the added to the winding N by the supply of an exciting input signal Is (or output signal), so that the Setting ac current from the high frequency voltage e, the resultant tion is attained independently of the exciting signal cir magnetic field becomes Zero because of symmetrical ex cuit. citation. However, when the other direct current is Sup FIG. 15 shows an example capable of obtaining a plied to the output winding Na while the voltage e is being modulated voltage the phase of which differs by 180 in impressed on the exciting winding N, so as to distort the accordance with the polarity of the small or weak input resultant magnetic field by adding a direct magnetic field signal. In the circuit of FIG. 15, an input winding N1, 5 5 Hs to the fields Hi and H, then, as shown in FEG. 18(c), an output winding N, an exciting winding N for Supply a direct current magnetic flux (), and second harmonic ing a high frequency current it having frequency f1, magnetic fields b, and the will appear, whereby the har and the other exciting winding N for supplying the other monic osciliation of the double frequency of the voltage high frequency current it having frequency f2 are wound e Such as shown in FIG. 18(d) is produced and, more 60 over, the phase of the oscillation is controlled to be 0 on four ferro-magnetic cores M1, M2, M3, and M4 so that phase or it phase in accordance with the polarity of the the winding polarities of the coils of all the windings are direct current Supplied to the winding N, that is, in ac the same on one core M1, the number of coils having the cordance with the direction of the direct current magnetic same polarity is equal to those having reverse polarity field Hs applied to the magnetic cores M and M. (FIG. 18 on the other three cores M2, M3 and M4, and the wind 65 shows the case, in which said direction is --). ing polarities of all coils of one winding Na are the same, Generally, when a ferromagnetic core is placed in a and each of the other three windings N1, N2 and N con magnetic field H, the relation between said field H and sists of coils of positive and negative polarities, the nun the magnetic flux is occurring in the magnetic core is ber of coils of positive polarity being equal to that of represented by the following Equation 1. the coils of negative polarity. Now let it be assumed O that the magnetic hysteresis characteristics of the four Where (ox) and (3) are non-linear coefficients cores are the same. Then, when the input current Is f(p) = cqb-6p3 (1) and the exciting currents it and it2 are simultaneously applied a resultant voltage efit-fo having frequency When, as described above, a parametrical oscillation is (f-tf) is induced at the output terminals 7 and 8 of the established, an approximate value of a parametrical oscil 3,191,053 - 2 lation rate p which represents the strength of said oscil hysteresis loop, so that the hysteresis loss decreases re lation is represented by the following Equation (2). markably. Accordingly, even when four magnetic cores are used, the hysteresis loss becomes lower than % of that of the case (FIG. 16) in which two magnetic cores are p = K. Each (2) used. Furthermore, when each magnetic core is excited in one direction, the apparent residual magnetism is weak. abot (+)-d) Accordingly, it is possible to control by the application wherein p=gpo-gb1, and K is a constant determined by the of a setting signal to the winding Ns, the phase of the condition of the circuit. One the other hand, since, in second high harmonic oscillation of the exciting current conventional ferro-magnetic or ferroelectric elements, O double frequency by means of a relatively weak direct c.)>{8, and a large imaginary power is necessary for the current, without carrying out demagnetization by supply generation of an oscillation. In the ferromagnetic or of a setting signal current, ferroelectric element having a substantially rectangular Of course, it is clear that when a damped oscillation hysteresis characteristic, oxidg, and imaginary power is wave is impressed on the winding N of FIG. 19 before small, but the coercive force. He is large, so that the sign detection operation it is possible to discriminate a hysteresis loss is large, whereby the parametric oscillation further small signal sign. of the double frequency of the exciting current is made The above illustration of FIG. 19 relates to a system in difficult and the power conversion gain is made small. which the parametric oscillation factor p is forcibly en Accordingly, if it is possible to make (3 large by the use larged by enlarging coefficient 3 of the Equation 2. More of a ferro-magnetic or a ferro-dielectric body having the 20 over if the parameter ox is decreased, the parametric os character (a)->6), or to diminish ox or eliminate ca, it is cillation can be more effectively attained, as will be clear possible to make the parametric oscillation rate p large. from the Equation 2. This example is shown in FIG. The following example of FIG. 19 is based on the just 20, in which two pairs of the magnetic cores (M1, Ms) mentioned consideration. and (M2, M4) are provided and their winding method The circuit of FIG. 19 comprises an input and output is different from the example as shown in FIG. 19. That winding Na consisting of four coils which are connected is, a first exciting winding N1 consists of two coils which in series and wound, respectively, on four cores M1, M2, are connected in series, one of which is wound on the Ms, and MA in the same polarity; a first exciting winding core M1 is the same polarity as that of the coil of the N1 consisting of two coils (11 and 2) which are con winding Na wound on said core M1, and the other of nected in series, one (11) of which is wound on the core 30 which is wound on the core M in the reverse polarity M1 in the same polarity as the coil (21) of the winding to that of the coil of the winding N wound on said N2 which is wound on said core M1, and the other coil core M3. A second exciting winding N1, consists of (12) is wound on the core M2 in a polarity reverse to two coils which are connected in series, one of which is that of the coil (22) of the winding N which is wound Wound on the core Main a reverse polarity to that of the on the core M2. The coils (11 and 12) are connected in 3 5 coil of the winding Na wound on said core M, and the series. A second exciting winding N1 consisting of two other of which is wound on the core M in the same coils are connected in series, one of which is wound on polarity as that of the coil of the winding N wound on the core M in a reverse polarity to that of the coil of said core M4, and a direct current winding N for elemi the winding N2 wound on the core M, and the other of 40 nating the linear coefficient a is wound on the cores M1, which is wound on the core M4 in the same polarity as M2 in the same polarity as the winding N and, on the that of the coil of the windings N wound on the core cores M3 and M4, in the reverse polarity relative to the M4; and a setting winding N consisting of two kinds of winding N. coils which are connected in series, one kind of which In the example of FIG. 20, when, as in the case of is wound on the cores M and M in the polarity reverse F.G. 19, a half rectified exciting current is supplied to to that of the coils of the winding N which are wound the windings N and N1", respectively, through recti on said cores, and the other kind is wound on the cores fiers D1 and D2 while a direct current is being supplied M2 and M4 in the same polarity as that of the coils of the to the winding Na, the following condition is established. winding Na which are wound on the cores. The coil of the first winding N1 wound on the core M In the circuit of FIG. 19, when rectifiers D and D are is is of reverse polarity with respect to that of the core connected, respectively, to the windings N and N' as M3, and the coil of the second winding N' wound on shown in the drawing, a condenser C is connected in the core M2 is reverse with respect to that of the core parallel to the winding N2, and an exciting voltage e is M4, and the coils of the direct current winding N wound impressed to the windings N and N1, the circuit reso on the cores M3 and M4 are of reverse polarity with nates with the second harmonic of the exciting current. 5 5 respect to that of the coils of the winding N wound on According to the circuit of F.G. 19, two pairs of the the cores M1 and M2, so that variation of the magnetic magnetic cores M1, M2 and M3, Mia are, alternately ex field applied to the cores viewed from the input and out cited, as shown in FIG. 17(c) by waves H. H., H., H. put winding Na takes, as shown in FIG. 17(d), such per rectified half wave of the exciting current. However, forms obtained by Superposing of the direct current mag the resultant magnetic field viewed from the secondary 60 netic fields --Ha and -Ha on the half wave rectified side, that is, from the side of the winding N becomes exciting magnetic fields H1, H., H and H. Accordingly, equal to that of FIG. 17 (b). Accordingly, when a if the value of the direct current to be supplied to the direct current signal is impressed on the input and output winding 4, that is, the intensity of the field td is suit winding N2 by means of the same exciting operation as ably selected, this case becomes equivalent to the case in in the case of FIG. 16, an oscillation of the double fre which an exciting magnetic field as shown in FIG. 17(f) quency of the exciting current the phase of which is is applied to the hysteresis characteristic such as shown controlled to be 0 or it in accordance with the polarity in FIG. 17(e), obtained by reducing substantially or of the exciting current will occur. eliminating the straight portion of the d-H characteristic However, in each magnetic core, only either of the of FIG. 17(a). - rectified half waves of the exciting current is impressed, 70 Accordingly, when in this condition a small direct and the reverse wave is not impressed, so that a higher current signal is impressed on the input and output wind order harmonic component that is, the coefficient 6 in ing Na So as to distort its symmetry, a second high har creases remarkably thereby increasing the parametric ex monic oscillation of the exciting current can be produced citation rate p as will be understood from the Equation as in the case of the example of FIG. 17. According to 2. Moreover, a loop is described at one side of the 75 this system, the phase of the oscillation of the second 8,191,053 3 t high harmonic can be controlled by impressing a very elements an output signal having a frequency equal to the Small direct current signal on the input and output wind Second high harmonic component of the exciting signal ing Ng. and having one of two possible opposite phases in accord The above description relates mainly to the case in ance. With an algebraic sign of an algebraic difference be which ferromagnetic elements are used. However, the tween said input signal and said reference standard signal, same result as above can be obtained by using ferro Said output means having tuning means for resonating electric elements, but in this case, it is only necessary with said second high harmonic component. to replace electric current and magnetic field respectively 2. An electric sign detecting system as claimed in claim by electric voltage and electric field. 1, wherein said setting means comprises terminal means As will be understood from the above description, by O for applying an alternating-current signal having a grad utilizing only the minor portion of the hysteresis loop, ually damped termination as said setting signal. by and carrying out only one-side excitation, it is pos 3. An electric sign detecting system as claimed in sible to decrease hysteresis loss and to facilitate non claim 1, wherein said exciting means comprises exciting Symmetrical oscillation. Accordingly, this system can be terminal means for receiving an alternating-current and a effectively applied to any logical operation, analog digital 5 direct current bias signal as said exciting signal. converter, etc. 4. An electric detecting system comprising, two ferro All of the above examples relate to cases in which the magnetic cores having hysteresis characteristics substan electric signals to be detected have been sampled. How tially symmetrical with respect to their original point, an ever, the present invention can be applied, with the same input winding having two input coils wound respectively effect, to the case in which a continuous electric signal on the cores and connected in series for applying simul is used. taneously both an input signal and a reference standard Now, considering the case in which a continuous input signal, an exciting winding having one coil wound on one signal current is supplied as a signal current, in each of the cores in the same winding direction as the input magnetic core, the alternating current for demagnetizing coil wound on the core and the other coil wound on the the residual magnetism to set the core becomes an alter cther core of the cores in the reverse winding direction nating bias current, thus producing a residual magnetism to the input coil wound on said other core for applying or a magnetic polarization made to correspond to the a setting signal to remove the effect of the residual mag electric signal to be detected, whereby an alternating netism produced in the non-linear elements by preceding output signal, the polarity of which is converted to 0 phase signals applied thereto and for applying an alternating or it phase, will be obtained. current exciting signal, said one and said other coil being In the other cases, the same result will be obtained. connected in series, an output winding having two coils That is, even if a large magnetic field is impressed on non Wound respectively on the cores in the same polarity as linear element or elements so as to be perpendicular to the input coils and connected in series for taking out an fields caused by the input signal winding and the output output signal having a frequency equal to the second high winding, the residual polarization produced by such fields 3 5 harmonic component of the exciting signal and one of two is substantially directed to a direction perpendicular to possible opposite phases in accordance with an algebraic the field direction of the input winding. Accordingly, in sign of an algebraic difference between said input signal this state, if an input signal and an exciting signal are and said reference standard signal, said output winding impressed on Such nonlinear element or elements, a mean being connected with a capacitor for resonating with the value of magnetic flux is established in a plus or minus 40 Second high harmonic component. state in accordance with the polarity of the input signal 5. An electric sign detecting system comprising, two without relation to the preceding hysteresis phenomenon. ferromagnetic cores having hysteresis characteristics sub Then, when an alternating exciting current I of fre stantially symmetrical with respect to their original point, quency f is supplied after cancelling the resultant residual an input winding having two input coils wound respec magnetism or polarization directed to the input signal tively on the cores and connected in series for applying winding an output winding as described above, an al an input signal, a reference winding connected in said ternating-current output of frequency 2f the phase of System identical to the input winding for applying a refer which becomes 0 phase and it phase in accordance with ence standard signal, an exciting winding having one coil the polarity of the electric signal to be detected will be Wound on one of the cores in the same winding direction obtained. 50 as the input coil wound on the core and the other coil As described in detail above, in the detecting circuit Wound on the other cores in the reverse winding direc of the present invention, only the symmetrical character tion to the input coil wound on the other core for apply of the elements is utilized, and the other conditions have ing a setting signal to remove the effect of the residual no direct relation to the signal discrimination. Moreover, magnetism produced in the non-linear elements by pre ince symmetricity of the characteristics of the non-linear 5 5 ceding signals applied thereto and for applying an alternat elements such as a ferromagnetic or ferrodielectric body Ing-Current exciting signal, said one and the other coil is not distorted by the outside physical conditions. In being connected in Series, an output winding having two stability due to variation of the character of the non-linear coils Wound respectively on the cores in the same polarity element is reduced in comparison with conventional de as the input coils and connected in series for taking out tecting devices, whereby a stable and precise sign detec 60 an output signal having a frequency equal to the second tion of a signal can be made possible. high harmonic component of said exciting signal and cine What we claim is: of two possible opposite phases in accordance with an it. An electric sign detecting system comprising, an algebraic sign of an algebraic difference between said in even number of non-linear elements each having hysteresis characteristics substantially symmetrical with respect to put signal and the reference standard signal, a capacitor their original point, input means for applying an input connected to said output winding for causing resonating signal to said non-linear elements, setting means for ap With said Second high harmonic component. plying to said non-linear elements, prior to the applica 6. A plurality of electric sign detecting devices, in tion of the input signal, a setting signal to remove the ef combination, each as claimed in claim 1, in which all of fect of residual polarizations produced in the non-linear the windings other than said output winding are the same elements by preceding signals applied thereto, a reference and Said Windings including said output winding are re standard signal simultaneously with the application of said Spectively connected to one another in series, said refer input signal, exciting means connected for applying to ence winding having a number of turns Successively in said non-linear elements an alternating-current exciting Creasing whereby the input signal is converted to a signed signal, output means for taking out from said non-linear 75 signal quantized by a respective algebraic sign detecting 3,191,053 5 A6 device in the state of the particular phase of the second OTHER REFERENCES high harmonic of the exciting signal. 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